University of California
Ucmp: The Paleozoic Era
An excellent overview of the Paleozoic Era. It also provides a chart where you can learn information regarding each of the time frames within the era.
University of California
Ucmp: Web Geological Time Machine
The Museum of Paleontology at Berkeley offers an online geological time machine which allows you to catch a glimpse of ancient eras in earth's history. Click into an "Era" to learn about its stratigraphy, life forms, localities, and...
Encyclopedia of Earth
Encyclopedia of Earth: Geology: Silurian
Article covering the Silurian Period, which lasted from 443 million to 417 million years ago. It covers the subdivisions of this Period, some life forms preserved in the fossil record, geology, and climate. (Published: January 22, 2010)
University of California
Ucmp: The Silurian Period
Provides a brief overview of the Silurian Era, links to specific information during the era, and a chart of the major subdivisions of the Silurian Period.
PBS
Nova: A Brief History of Earth
This timeline is a good resource if you are looking for brief descriptions of the geologic periods. Descriptions include pictures of common organisms for each period and the range of time covered by each period.